In existing wireless technologies, signal repeating devices, such as repeaters or distributed antenna systems (DAS), are used to extend the coverage of an overall wireless system beyond the ranae of traditional base stations. For example, an overall wireless communication system may consist of a plurality of base transceiver stations (BTS) or base stations that communicate with each other and with user equipment, such as cellular phones, to provide a defined coverage area. In such coverage areas, there are often smaller geographical areas that have very low signal coverage, as provided by one or more of the base stations. For example, such areas of low signal coverage may be within buildings or in areas that are otherwise obstructed, such as by terrain features or man-made structures. Rather than simply implementing another costly and large base station to provide coverage in such low signal areas, repeaters and distributed antenna systems are often utilized.
While repeaters and distributed antenna systems (herein collectively, “signal repeating systems”) may adequately extend coverage, it may be desirable to eventually install a dedicated BTS in order to increase the amount of capacity offered in the area. To that end, it is desirable to be able to determine the relative loading and traffic of a signal repeating system so that a building owner or other system operator is aware of the traffic requirements for that wireless environment.
One method of detecting traffic within a mobile network is to utilize the receive signal strength indication (RSSI) measurement of the power that is present in a received radio signal. The RSSI is a well-known parameter in the operation of signal repeating systems. The RSSI-based detection method for determining traffic within a wireless environment or network is used extensively in GSM repeaters and distributed antenna systems. Usually, the uplink RSSI is utilized to determine the uplink traffic from mobiles that are within the coverage range of a signal repeating system. The signal repeating system identifies the channels used by the adjacent base stations and it then distributes and amplifies the signals in order to monitor the equivalent uplink (UL) frequencies. If the RSSI level on a UL channel exceeds a certain threshold, the system can detect the UL traffic. The threshold level is usually a level above the receiver input noise floor for the signal repeating system. The specific delta with respect to the noise floor depends upon the acceptable probability of having false positive detections, which might be triggered by regular thermal noise peaks. In addition to the independent measurement of the RSSI levels, the signal repeating system can determine the RSSI within a certain timeslot by synchronizing itself with the base station through the detection of the downlink (DL) signal. Therefore, for such a gated RSSI measurement, the repeater or distributed antenna system can measure UL activity on a timeslot-per-timeslot basis.
However, while such a methodology works adequately for GSM repeaters and distributed antenna systems, the implementation of such a traffic detection and measurement system in a spread spectrum environment, such as CDMA or WCDMA, is more difficult. Generally, in a CDMA or CDMA network, the mobile devices or other user equipment (UE) devices are driven so that the transmit power is controlled in order to be close to or below the noise level of the receiving base station. In a typical configuration, the repeater or distributed antenna system operating in such a network essentially acts to extend the UL receiver of the base station. In that regard the repeater/DAS experiences the same low level receive signal from the user equipment devices. That is, the receive signal level from those devices is at the noise level, or even below the noise level, for the repeater/DAS. As such, this makes the use of RSSI-based uplink traffic detection and measurement generally unfeasible for such networks.
There are other mechanisms for determining the uplink traffic within a CDMA system, but those mechanisms require the specific spreading codes that are used for the various uplink signals received from the mobile UE devices. However, those spreading codes are known to the base station system, and are not necessarily known by the repeater or DAS. Therefore, a system that incorporates uplink traffic detection that relies upon correlation with dynamically-assigned uplink spreading codes generally will not be a feasible alternative for detecting and measuring uplink traffic within a repeater or DAS.
Accordingly, there is a need for providing a traffic measurement system for a repeater/DAS that can adequately detect and measure the uplink traffic within a spread spectrum network, such as a CDMA or WCDMA network or another network where the UL signal is at or close to the noise level of the system.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with a general description of the invention given below, serve to explain the principles of the invention.